[Coco] PSA / warning for all RGB2VGA owners

[Zippster]

Hi guys,  this is a PSA / warning for all RGB2VGA owners.

It has been brought to my attention by Roger Taylor on the Facebook group
that the RGB2VGA design has pin 9 of the outgoing VGA connector tied to ground.
This is the case with both Luis’s original boards, and the SE version (the circuit was
not changed, just layout and routing).  Many VGA pinouts show this pin as grounded, 
many as no connects, and some as +5V.

Pin 9 is used in some display standards (notably DDC1 and DDC2) to provide +5v from
the graphics adapter to the display to read an EDID rom with information about the
display even when not powered.  The standard calls for this rom to be powered by
the display when it’s on, so there is the potential that this supply could be connected
to ground when using the RGB2VGA board with a cable that has a through connection
on pin 9.

Many, if not most VGA cables appear to have no connection on pin 9, presumably for
this reason.  I would guess (hope) most displays using this feature would also have some
kind of current limiting in place for this situation, as pin 9 is shown grounded in so many pinouts. 

I have heard of no issues so far, but to be on the safe side… 

USE THE RGB2VGA ADAPTER ONLY WITH VGA CABLES THAT DO NOT HAVE A CONNECTION ON PIN 9

If there is no cable through-connection on pin 9, then this is not an issue at all.

Thank you,

- Ed